Is Antigone portrayed in the play as a feminist?

The simple answer is no. Let me explain.
Let’s assume that by “feminist” you mean an adherent or follower of feminism. According to the Oxford English Dictionary, feminism is the “advocacy of women's rights on the ground of the equality of the sexes.” Nowhere in Sophocles’s tragedy Antigone does the titular character advocate, promote, or sacrifice for women’s rights. Rather, Antigone martyrs herself for the right to offer traditional burial rites for her dead brother Polynices.
To quickly recap the relevant plot points of the play, Polynices was killed in battle when he betrayed his city-state and attacked Thebes with a foreign Argive army. This act of treachery led Creon, the newly appointed king, to issue a decree forbidding the burial of the traitor, declaring that “he must be left unburied, his corpse carrion for the birds.” He declares that the supreme loyalty every citizen of Thebes owes is to the state by saying, “Never at my hands will the traitor be honored above the patriot” and that anyone who breaks his command will be promptly executed.
Antigone puts Creon, her uncle and future father-in-law, in an awkward situation when she disobeys the proclamation, buries her brother, and is caught red-handed in the crime. Although Antigone’s death sentence is commuted, Creon banishes her to a cave. Antigone hangs herself in the prison before stubborn Creon, who finally accepts the advice of his son and the prophet Tiresias, can release her from the cavern. There is not a single moment in Sophocles’s play where Antigone strives for gender equality or women’s rights. She nobly defends her family, but there simply isn’t enough evidence to confidently declare Antigone a feminist as we understand the term today.
However, that doesn’t mean that Sophocles’s Antigone can’t be viewed from a feminist literary lens. Ancient Thebes is a staunchly patriarchal society. This can be seen in Creon’s attitude toward Antigone when he advises his son Haemon to “never lose your sense of judgment over a woman” and tells him to forget Antigone because “there are other fields to plow.” The insinuation is that women are worthless and viewed as sexual objects by the powerful in Theban society. Haemon, in his response, abuses his father by calling him “a woman,” one of the worst insults he could muster. Even the women understand their lowly position in Thebes. Ismene, in her attempt to dissuade her sister Antigone from burying their brother, encourages her to “remember we are women; we’re not born to contend with men. Then too, we’re underlings, ruled by much stronger hands.” Thebes is basically a feminist’s nightmare!
However, Antigone rebels against this patriarchy in ways that would have been shocking for ancient Greeks. Unwilling to be cowed by powerful men, Antigone courageously adheres to her values by burying Polynices even though she understands it might result in her execution. Even when caught, Antigone remains defiant, declaring that she is “not ashamed for a moment.” This courage, particularly from a woman, gains the approval of the Chorus and wins the popular opinion of the Theban citizenry. In this sense, the character of Antigone models feminist values of courage, independence, and a willingness to defy male authority.
In short, although Antigone cannot be called a feminist, because she does not fight for women’s rights or gender equality, she does embody many of the qualities of feminist philosophy.